Return of the Mighty Pygmy Rabbit

After sitting on the edge of extinction, North America’s smallest rabbit is taking short hops toward a rebound in Washington State

03-11-2013
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Anne Bolen

IN SPRING, ANIMALS EVERYWHERE are doing their best to breed like rabbits and pass on their genes. Well, maybe not. In central Washington State, the pygmy rabbit is barely holding on, in spite of a reintroduction program trying for more than a decade to rebuild this near-extinct subpopulation. Recently, however, researchers have taken a leap of faith that might turn this critter’s last stand into a short hop toward rabbit recovery.

Penny Becker, a conservation biologist at the Washington Department of Fish and Wildlife (WDFW), is among the many biologists, geneticists, veterinarians, managers and conservationists who have worked on this program. She says that while the latest results have been positive, “This is our last chance.”

Tiny But Tough Rabbits

Pygmies are North America’s smallest rabbit, with adults weighing less than a pound. Although tiny, they are tough. Their short legs can hop at speeds of 15 miles an hour. They are active year-round in temperatures ranging from below zero to more than 100 degrees F. Equipped with long claws, they are the only U.S. rabbits to dig their own burrows. Females protect their litters by burying them in shallow burrows, returning only once a day to uncover and nurse their kits before reburying them. This continues for just two weeks, when juveniles are able to fend for themselves.

In 2001, a statewide survey found fewer than 30 pygmies, all in one county of Washington’s Columbia Basin. Researchers captured 16 of them for breeding programs at the Northwest Trek Wildlife Park, Oregon Zoo and Washington State University in the hope the resulting kits could seed a wild population. However, the effort was already challenged because, unlike other rabbits that can breed almost year-round, pygmies have a shorter breeding season, from February to July, and females only produce one to three litters of three to six kits each year. Yet the captive rabbits seemed reluctant to mate at all, and many of the kits that were born suffered from inbreeding problems such as weakened immune systems and bone deformities.

“We worked with them every day, trying to keep every one alive, our students sometimes hand-feeding babies the size of a mouse,” says Rod Sayler, a conservation biologist who helped with the program at Washington State University. Although “those rabbits have broken our hearts thousands of times,” he says, “we don’t think we failed.” Rather, the researchers took what they learned about these unusual animals in captivity to their natural habitat, the sagebrush steppe.

Dependent on Sagebrush

Pygmies have adapted to live in arid sagebrush habitat over millennia. Most live in sagebrush prairie deserts and plains in the Great Basin. At least 10,000 years ago, glacial movements isolated the Washington subpopulation and made it genetically distinct. Because pygmies have larger livers than most rabbits, they can eat the sagebrush’s pungent, bitter leaves. “Sagebrush is pretty toxic stuff unless you evolve to digest it,” says Chris Warren, who is heading the U.S. Fish and Wildlife Service’s participation in the program. This plant’s leaves make up to 99 percent of the rabbits’ winter diet and are more than half of what they eat in summer. The animals also need the sagebrush’s scraggly, intertwined branches for cover and the deep soil around its roots for burrowing.

Since European settlement, however, the sagebrush-steppe habitat that once stretched like a sea across 155 million acres in North America has declined more than 30 percent. Farmers, ranchers and developers have cleared sagebrush from their land, and nonnative plants such as cheatgrass have overrun much of it. Sagebrush is also slow to recover from catastrophic fires, which have increased in the West in recent years. Central Washington, where pygmies historically lived, has been heavily developed and commercially farmed. “Pygmy rabbits can’t use those converted sites,” says Warren. “We are relying on the scattered habitats that are left.”

By 2004, all Washington’s wild pygmies were believed extirpated. Although the recovery team had already brought in rabbits from Idaho to strengthen the captive gene pool, the last genetically pure Columbia Basin pygmy rabbit died in 2008 at the Oregon Zoo. In 2011, the team decided the program needed a change to a more natural venue.

Born to be Wild

During 2011 and 2012, Becker and her colleagues added 73 wild rabbits translocated from Nevada, Oregon and Utah to their breeding population and released all the rabbits into two 6-acre and 10-acre enclosures in WDFW’s Sagebrush Flat Wildlife Areain central Washington, where the last wild pygmies had been found. The screened pens offered protection from terrestrial predators, and the burrows were covered with nets to avert aerial predators.

After the 2011 breeding season, 42 juveniles were released into the wildlife area, of which the team estimates about 10 percent survived. In 2012, more than 150 kits were born in the enclosures and 104 juveniles were released, of which 38 have been found alive so far. Genetic testing has also revealed that two rabbits released in 2011 have produced four offspring.

Although the U.S. Fish and Wildlife Service listed Washington’s distinct population as endangered in 2003, the agency denied a petition to classify the species as such in 2010 because of a lack of long-term information. Janet Rachlow, a wildlife ecologist at the University of Idaho studying pygmies, says that while the extent of their range seems not to have shrunk, given the decrease in sagebrush habitat, most likely, pygmy rabbit populations have declined: “I think if we look at the species’ actual distribution, it would tell us a different story.”

The Importance of Lagomorphs

So why continue this uphill fight for this little rabbit? Lagomorphs—rabbits, hares and pikas—play a critical role as food for many predators, including owls, hawks, bobcats, lynx, foxes and humans. Given that pygmies mostly live within 200 yards of their burrows beneath sagebrush shrubs, Rachlow says researchers are also looking into their function as ecosystem engineers and whether their concentrated urine and feces help nourish these desert plants. Beyond this, Becker says, “We have a responsibility to try to bring these rabbits back because we are responsible for their demise.”

Patterned after a similar effort to restore California’s endangered riparian brush rabbit, the approach of simulating a wild environment could be good for other lagomorphs, as “at least a fifth of them are facing extinction,” says Andrew Smith, chair of the International Union for Conservation of Nature Lagomorph Specialist Group. In the United States, climate change is affecting the American pika’s cold mountain habitat, and sea level rise or even a hurricane could wipe out Florida’s endangered Lower Keys marsh rabbit. Invasive eastern cottontails have overrun the range of the New England cottontail. And the white-tailed jackrabbit, a western hare, is also thought to have declined because of the decrease in continuous sagebrush-steppe habitat.

Long-term survival of pygmy rabbits will depend on leaving “enough connected habitat for this species to survive,” says Becker. In the meantime, the future for Washington’s pygmies is looking a bit brighter. A third pen has already been built 12 miles away from the others for this year’s batch of translocated and Washington rabbits to intermingle. This will help prevent any single event, such as a fire or disease, from wiping out Washington’s only pygmy rabbits.

“Several years ago we were collectively holding our breath about what was going to happen with this population,” Warren says. “We are not out of the woods yet, but we are cautiously optimistic that we are on the right track. It is heartening to know that we have a shot at conserving this species in Washington.”

Video of captive pygmy rabbits.Washington Department of Fish and Wildlife

NWF Priority: Saving the Sagebrush Sea

Conserving connected sagebrush and grassland habitat is a Federation priority, as “The sage-steppe biome is an ecosystem essential to a lot of animals,” says Tom France, NWF’s senior director for western wildlife conservation. NWF recently commented on a national sage grouseconservation strategy that could benefit other sagebrush-dependent species such as pronghorn, sage sparrow and the pygmy rabbit. The Federation and the Washington Department of Fish and Wildlife have also coauthored Climate Change Effects on Shrub-Steppe and Grassland Habitats in Washington Stateto help this state prepare for the potential effects of climate change. See www.nwf.org/sagebrush for more information about the sagebrush sea.